Process for upgrading catalytically cracked gasoline



United States Patent M 3,044,950 PROCESS FOR UPGRADING CATALYTICALLY CRACKED GASOLINE George B. Swartz, Jr., Penn Hills, Pa., assignor to Gulf Research & Development Company, Pittsburgh, Pa., a corporation of Delaware Filed Dec. 15, 1958, Ser. No. 780,576 4 Claims. (Cl. 208-57) invention relates to a process -for upgrading olefinic gasoline and more particularly to a process for con verting catalytical-ly cracked gasoline to gasoline of higher octane rating, and especially of higher motor method octane rating, by a combination of hydrogenation and catalytic reforming of selected fractions.

For a number of years the olefinic gasoline obtained by catalytic cracking of hydrocarbon oils has satisfied the demand for gasoline blending stock of reasonably high octane rating. However, the increased use of high compression automobile engines has so greatly increased the demand for gasoline of very high octane rating, that it has become desirable to develop methods for further up grading catalytically cracked gasoline so that the total gasoline pool can be raised to the required high octane level. Heretofore, processing of catalytically cracked gasoline for octane improvement has been very limited. For instance, catalytic reforming of such stocks has not been successful because the high olefinic content causes rapid deactivation of reforming catalysts, and especially of platinum catalysts. Hydrogenation of the olefinic gasoline merely lowers the octane rating by forming saturated hydrocarbons of lower octane value than the olefins. I have now developed a process whereby catalytically cracked gasolines can be efliciently and economically upgraded to a motor fuel of very high octane rating. My new process is based on the discovery that the combination of hydrogenation and reforming of selected fractions of the catalytically cracked gasoline can produce in high yield a product of higher octane number, especially of higher motor octane number, than the untreated catalytically cracked gasoline.

In this discussion I will use the short terms motor and researc to designate the octane ratings determined by the standard ASTM tests, namely, the Test for Knock Characteristics of Motor Fuels by the Motor Method (ASTM D357) and the Test for Knock Characteristics of Motor Fuels by the Research Method (ASTM D908).

High research octane number is desirable for city driving at low engine speeds and with frequent acceleration, but high motor octane number is desirable for highway driving at high engine speeds. The catalytically cracked gasoline is not suficiently high in motor octane rating for present and expected future demand. I shall also refer to clear octane numbers and leaded or +3 cc. TEL octane numbers. The clear octane number is the'rating of the gasoline without anti-knock additives and the leaded or +3 cc. TEL octane number is the octane rating of the gasoline to which tetraethyl lead has been added in the amount of 3 cc. per gallon of gasoline.

In general, my new process for upgrading an olefinic cracked gasoline comprises hydrogenating at least a residual fraction ofthe olefinic gasoline having an initial boiling point of 290 to 320 F. The hydrogenated residual fraction is subjected to a separation procedure which is selective for separating aromatics from nonarornatics. A hydrogenated fraction enriched in aromatics and a hydrogenated fraction enriched in nonaromatics are recovered. The fraction enriched in nonarornatics .is subjected to catalytic reforming to produce a reformate of Ice the fraction enriched in aromatics and with other fractions obtained from the cracked gasoline to produce a gasoline having a considerably higher motor octane rating than the untreated catalytically cracked gasoline.

The charge stock for my process is a full range catalytically cracked gasoline. This type of gasoline is produced by contacting a cracking charge stock, for example, a straight run gas oil, at high temperature, e.g., 8S0- 1000 F., with a cracking catalyst, such as a synthetic silica alumina composite maintained in a fixed, fluidized or moving bed system. Usually a yield of 40 to 50 percent of olefinic gasoline is produced. The cracked gasoline product will boil in the range, for example, from 100 to 430 F. and will have an olefin content from 15 to volume percent. The research octane number of catalytical-ly cracked gasoline will normally be rather high, for example, from about 89 to clear, or 94 to 101, leaded. However, a characteristic of such gasolines is that the motormethod octane rating is rather low, for example, from 12 to 16 points lower than the corresponding leaded or clear research octane rating.

I will now describe my invention with reference to the drawings, of which FIGURES 1 through 4 are schematic flow diagrams of four different embodiments of my process.

In the embodiment of my process illustrated by FIG- URE 1 the entire full range cracked gasoline is subjected to hydrogenation and fractions of the hydrogenated product are then treated separately. As the drawing shows, an olefinic gasoline such as the gasoline produced by fluid catalytic cracking, otherwise referred to as an FCC gasoline, is charged by line 10 to a hydrogenation unit 11. In the hydrogenation unit the cracked gasoline in admixture with hydrogen is contacted with a hydrogenation catalyst such as a catalyst composed of minor amounts of the oxides of cobalt and molybdenum supported on an alumina carrier. The hydrogenation conditions include, for example, a hydrogen concentration from about 1,000 to 10,000 standard cubic feet per barrel of hydrocarbon (abbreviated hereinafter as s.c.f./bbl.), a temperature of 500 to 800 F. and a pressure of 200 to 800 pounds per square inch gauge (abbreviated hereinatter as p.-s.i.g.). The hydrogenation treatment saturates substantially all of the olefins and desulfurizes the cracked gasoline. More specifically, the hydrogenation reduces the bromine number of the fraction treated to 5 or less and reduces the sulfur content to less than 0.01 weight percent.

In the embodiment of FIGURE 1 the hydrogenated full range olefinic gasoline is fractionally distilled in column 12 to produce three fractions: a light fraction with drawn overhead by line 14 having a boiling range from the initial boiling point (IBP) of the charge to an end point (EP) of to 195 F.; a middle or intermediate fraction withdrawn by line 15 having an initial boiling point of about the end point of the light fraction (175 195 F.) and an end point of 290 to 320 F.; and a bottoms or residual fraction withdrawn by line 16 boiling from about the end point of the middle fraction (290- 320 'F.) to the end point of the charge. Specifically, FIGURE 1 illustrates an embodiment of the process in which the three fractions are an IBP180 F. light frac Patented July 17, 1962 this fraction is passed directly to gasoline blending unit 17 without further treatment.

The middle fraction withdrawn by line is subjected to catalytic reforming in the reforming unit 18. This is the conventional catalytic reforming in which the gasoline in admixture with hydrogen in a concentration, for example, from about 1,000 to 20,000 s.c.f./bbl. is contacted at a temperature from 800 to 1050 F. and a pressure from 250 to 1000 p.s.i.g. with a reforming catalyst such as platinum on alumina, molybdenum oxide on alumina, or the like. The previous hydrogenation of the middle fraction is effective to reduce its olefin and sulfur content to an extent that the hydrogenated fraction is an excellent reforming charge stock, even when using the sensitive platinum-alumina catalyst. The reformed product of high octane rating is withdrawn by line 19 and passed to the gasoline blending unit 17.

I have discovered that the hydrogenated 290-320 F. IBP residual fraction of the cracked gasoline has a large content of high octane rating aromatics. Consequently, I subject this fraction to a separation procedure which is selective for separating aromatics from nonaromatics. As illustrated in FIGURE 1, a suitable procedure is to charge the fraction to a solvent extraction unit 20 wherein the fraction is contacted with a suitable solvent such as diethylene glycol according to the known procedure to produce an extract fraction enriched in aromatics and a ratfinate fraction enriched in nonaromatics. The extract fraction enriched in aromatics has a high octane rating and is passed by line 21 to the gasoline blending unit 17. The raffinate fraction enriched in nonaromatics is of low octane rating and is passed by line 22 to the catalytic reforming unit 18 in admixture with the hydrogenated middle fraction. The products of each of the described operations, namely, the hydrogenated light fraction of high motor octane rating withdrawn by line 14, the reformed hydrogenated middle or intermediate fraction and the reformed hydrogenated rafiinate Withdrawn by line 19, and the hydrogenated aromatic extract withdrawn by line 21 are blended to produce a gasoline of very high research and motor method octane ratings.

Although the principles of my invention can be applied to the procedure such as shown in FIGURE 1 in which the full range cracked gasoline is hydrogenated, in other embodiments of my process only selected fractions of the cracked gasoline are hydrogenated. FIGURE 2 is a flow diagram of an embodiment of the process in which the olefinic gasoline, such as an FCC gasoline, Without being previously hydrogenated, is fractionally distilled in column 24 into three fractions. FIGURE 2 illustrates a specific operation in which the three fractions are: an IBP-180" F. light fraction withdrawn overhead by line 25; a 180- 310 F. intermediate fraction Withdrawn by line 26; and a 310 F.end point residual fraction Withdrawn by line 27. However, the end point of the light fraction and the initial point of the intermediate fraction can range from 175 to 195 F. The end point of the intermediate fraction and the initial point of the residual fraction can range from 290 to 320 F. The light olefinic fraction which is composed mainly of C and C hydrocarbons is passed by line 25 to a hydrogenation unit 28 and is subjected to catalytic hydrogenation, as previously described. Although hydrogenation of this chiefly C -C fraction does not appreciably improve its research octane number, I have discovered that it does improve its motor octane number. Consequently, by hydrogenation alone and without reforming, the value of the light fraction of the olefinic gasoline can be improved. The hydrogenated light fraction is passed by line 29 directly to the gasoline blending unit 30.

The intermediate fraction of the FCC gasoline withdrawn by line 26 is of reasonably high octane number as separated from the full range gasoline and is passed to the blending unit 30 without further treatment.

In accordance with my invention the residual fraction withdrawn by line 27 is passed to the hydrogenation unit 31 and is subjected to hydrogenation in the manner previously described. The hydrogenated fraction recovered from hydrogenation unit 31 is then subjected to a selective separation process. For example, as shown in FIGURE 2, the hydrogenation product is passed to solvent extraction unit 32 and is contacted with a suitable extracting solvent such as diethylene glycol as previously described. An extract fraction enriched in aromatics is passed by line 33 to the gasoline blending unit 30. The raffinate fraction is enriched in nonaromatics and, having been hydrogenated previously to saturate olefins and remove sulfur, the fraction is an excellent reforming stock. The fraction is passed by line 34 to the catalytic reforming unit 35 and is subjected to catalytic reforming as previously described. The reformate of high octane rating is then passed by line 36 to the gasoline blending unit 30. The products of the various operations illustrated in FIGURE 2, namely, the hydrogenated light fraction, the

untreated middle fraction, the extracted aromatics fraction of the hydrogenated bottoms and the reformed raffinate fraction of the hydrogenated bottoms are blended to form a gasoline having a high research and motor method octane rating.

In a variation of the flow scheme of FIGURE 2 the light fraction from line 25 can be combined with the residual fraction of line 27 and the combined stream can be hydrogenated in a single hydrogenation unit 31. This eliminates the need for two hydrogenation units. However, the nonaromatics of the hydrogenated product are subsequently subjected to catalytic reforming in reforming unit 35. Since the hydrogenated light fraction has a high content of branched chain C -C parafiins it is not appreciably upgraded by catalytic reforming. The capacity of the reforming unit is, therefore, not most efficiently used when this hydrogenated light fraction is charged to it. If the light and residual fractions are combined and are hydrogenated in the same hydrogenation unit, it is preferred to fractionate the hydrogenation product, e.g., in a distillation column between the hydrogenation and extraction units, to separate a C C fraction which is sent directly to gasoline blending and a residual fraction which is passed to the solvent extraction unit. However, it is usually preferable to hydrogenate the light fraction separately and pass it directly to the gasoline blending unit as shown in FIGURE 2.

FIGURE 3 shows another embodiment of my process in which the full range cracked gasoline is fractionally distilled in column 40 into two fractions, a light fraction composed mainly of C -C hydrocarbons which is withdrawn overhead by line 41 and a bottoms fraction withdrawn by line 42. The end point of the light fraction and the initial point of the bottoms fraction will be in the range from 175 to 195 F. In the specific operation illustrated in FIGURE 3 the two fractions recovered from column 40 are an IBP180 F. light fraction and a 180 F.end point bottoms fraction. The light fraction, having a reasonably high research octane number, is passed directly to gasoline blending unit 43. The bottoms fraction is hydrogenated in hydrogenation unit 44 and the hydrogenated product is fractionally distilled into two fracoperation in which a 180-310" 'F. intermediate fraction is Withdrawn overhead by line 47 and a 310 Fa-end point bottoms fraction is withdrawn by line 48. The bottoms fraction is then treated to selectively separate aromatics from nonaromatics. For example, the fraction is subjected to solvent extraction in solvent extraction unit 49, as previously described. The extract fraction enriched in aromatics is of high octane rating and is'passed by line 52 to the gasoline blending unit 43. The raifinate fraction enriched in nona-romatics is withdrawn by line 53 and is combined with the hydrogenated intermediate fraction of line 47 to form the feed for the catalytic reforming stage. These two fractions of low octane rating, having been hydrogenated to saturate olefins and remove sulfur, are excellent reforming stocks. The combined stream is passed to catalytic reforming in the reforming unit 50. The high octane reformate withdrawn by line 51 is passed to the blending unit 43. A final high octane product is obtained by blending the untreated light fraction, the ex tract fraction from the extraction stage, and the reformate obtained by catalytically reforming the hydrogenated intermediate fraction and the raffinate fraction from the extraction stage.

FIGURE 4 illustrates still another embodiment of my process in which the only fraction of the catalytically cracked gasoline to be subjected to further treatment is the residual fraction having an initial boiling point in the range from 290 to 320 F. FIGURE 4 shows a specific operation in which the FCC gasoline charged to distillation column 55 is separated into an IBP-3l0" F. fraction withdrawn overhead by line 56 and a 310 F.end point residual fraction withdrawn from the bottom of the column by line 57. The overhead fraction is passed directly to gasoline blending unit 58. The 310 F.end point fraction is subjected to catalytic hydrogenation in the hydrogenation unit 60. The hydrogenated product is then passed to the selective separation stage. For example, theihydrogenated fraction is passed to the oslvent extraction unit 61 and is extracted with a solvent such as diethylene glycol, as previously described. An extract fraction enriched in aromatics is withdrawn by line 62 and is passed to the gasoline blending unit 58. The

resulting fractions.

rafiinate fraction enriched in nonaromatics is passed by:

line 63 to the catalytic reforming unit 64. The reformate' of high octane rating is then passed by line'65 to the blending unit 58. A final product of high octane rating is formed by blending the untreated IBP310 F. olefinic fraction, the'reformate, and the aromatics-enriched extract fraction. Marked improvement in octane rating is thus obtained although only a minor part of the total cracked gasoline is subjected to the upgrading treatment.

EXAMPLE light and heavy FCC gasolines and had an ASTM boiling range from 112 to 380 'F., a gravity of 60.9' API, and a bromine number of 114. This gasoline was fractionally distilled to produce three fractions: an IBP-180 F. light fraction, a 180 F.310 F. intermediate fraction and a 310 F.end point residual fraction. The fractionation was carried out by a procedure substantially according to the procedure of a true boiling point distillation and in a manner that produced fractions similar to those obtainable in a conventional commercial tractionating column. This included using a fractionating column having a packed section, employing reflux and measuring overhead vapor temperature to determine the cut points. In this manner, the light fraction was obtained by collecting distillate until the overhead vapor temperature reached 180 F. The middle fraction was then obtained by separately collecting the next portion of distillate until the overhead vapor temperature reached 310 F. and finally the undistilled portion of the charge stock boiling below the cut point of 310 F. was collected as a residual fraction. V

Table I below provides inspection data for the full range FCC gasoline and for the three fractions thereof obtained by distillation as described in the above example.

Table 1 Fraction. Charge IBP180 F. 180310 F. 310 F.-EP

Yield, percent by Volume of Full-Range FOO Gasoline--- 100.0 41. 4 42. 6 15. 9 Inspections:

Gravity, API 60. 9 78.2 54.3 38. 6 Sulfur, percent by Weight 0. 091 0.042 0.124 0. 189 Bromine Number 114 160 106 44 Hydrocarbon Type, percent by Volume:

Aromatics- 52. 1 Olefins- 29. 4 18. 5

saturates...

N aphthenes- Parafiin Podbielniak Analysis, percent by Weight:

Butanes-Butenes 0. 2 Isopentane 4. 6 10. 5 n-Pentane 1. 4 3. 6 Pentenes 12. 8 31. 7 HeX-anes and Heavier.. 81. 0 54. 2 Reid Vapor Pressure Lb 5. 7 Dis itillation (ASTM D-86- Over Point, F 112 115 208 325 End Point, F 380 163 287 420 10% at: F 144 133 220 334 208 145 234 347 328 158 266 373 Motor Method- Clear 79. 0 81. 1 78. 4 80. 1 +3 cc. TEL 83.0 85. 6 82. 7 84. 2

Research Method- The table includes ASTM distillation data obtained by Table Il-Continned the procedure of ASTM D-86-54. It will be noted that {h Run Number 1 2 3 8 over y end Polnts p the ASTM f i l 9 Fraction Treated {BF-180%, 180-310F, 310I ,-EP do not co1nc1de with the cut points employed In distilling the FCC gasoline into three fractions as described above 4 Y to, V. P t

The disagreement is a result of lnherent limitations of hjntrea eli ii rao gfi Lig the ASTM distillation method. As is well known, the gg igg g- 104-4 102-9 101-3 ASTM mitial boiling point of a mixture will be 'consot b 863 54s 28s srderably higher than the initial boiling point as determined igg i, l. fgf 83 4 57 s 40 0 by true boiling point distillation and the ASTM end point S lfur, Percent y Wlll be considerably lower than the end point determined ,Y, 95 by true boiling point distillation. (See Perry, Chemical Hydrocarbon yp Engineers Handbook, 3d Ed., pages 606-607.) The T, ;,E,Pg fj fffi m M ASTM data are included because they are in some degree snm 0.5 1.9 3.4 helpful in characterizing the fractions. However, it 3f 3:; 13f; should be understood that in defining the fractions lfarflflins 8 -3 36- f d DistrllatmnQtSIM D- orme 1n my p1 ocess in terms of 1n1t1al boiling points and z end points, I refer not to ASTM distillation data but to ggg ggz gtj 2; 08 2;; the cut points that would be employed for obtaining such 10 pefcailt g jjjjj 112 215 330 a lons by atmospheric pressure fractionation of the 3% olefimc gasoline or hydrogenated fractions thereof in a rrno orilidifiimti'o'ro'ff typical commercial distillation column provided with g g 76 3 61 8 71 8 vapor-liquid contacting means such as packing or bubble +3 ooT'iTfiIIIII 9314 8117 e011 cap trays and employing normal reflux ratios. These 77 8 64 6 so 1 remarks apply also to the distillation data of the other +3 ooi E'LIIIII 93:4 84:9 9110 tables of this application.

The three fractions of Table I were subjected to catalytic 3 Cobalt-Molydenum on Alumina. hydrogenation over a fi d d cobalt molybdenum based on changemhydrocarbon composltlondurmg talyst at temperatures ranging from 635 to 678 F., a m a pressure of 600 p.s.i.g., a liquid-hourly space velocity of lable II Shows thaf; hydrogenation redflced the Octane about 2 volumgs f hydrocarbon Per volume of catalyst numbers of all fractions, except for raising the leaded per hour, and at a hydrogen rate of about 6,000 standard a Octane number light fraclloll fmm 855 to cubic f t per barrel of hydrocarbon The Catalyst had 93.4. The octane sensitivity, or the dlfierence between the following approximate composition: cobalt oxide, 2.8 research and number? 9 an fractlons was Weight percent; molybdenum Oxide, 141) weight percent; greatly reduced while lead susceptrbflity, or the octane Silica L6 Weight percent; and alumina, 8L6 Weight pep mprovement obtained by addition of tetraethyl lead, was cent. Further details of the reaction conditions for each lncreasedadfhtlon to the effect on motor and hydrogenation run and the yields and inspections of the sfimch fatlllgs, as Shown Table yd g hydrogenatgd products are given i Table 11 below tron of the light fraction resulted in anrarked unprove- 40 ment of the road performance characteristics of the leaded Table II light fraction when tested In premium gasoline blends in 1 2 3 five automobiles with high compression engines. F EiZ E iBZZiTJdIIIIIIIIII rnr-ison 180-3l0F. awn-Er I have further subjected h hydrogenated t ns of Table II to catalytic reforming. The catalyst for these Operating Conditions: runs was a pelleted, fixed-bed, platinum-alumina catalyst igg g g (l) (1) 0) containing essentially about 0.6 weight percent platmum, eroiure, F. 635 678 6 0.5 weight percent chlorine and 98.9 weight percent alu- "fffj fj Z0 20 mina. The reaction conditions included temperatures of g rgs- 600 50 about 900 and about 950 F., pressure of 300 p.s.i.g., hire-notion Rate, space velocity of 2 volumes per volume of catalyst per ig' fis gg g g 5810 5950 hour and hydrogen concentration ranging from about Pe e y 66 3 68 7 a 1,000 to 7,000 s.c.f./bbl. Details of each of the reforming nleedo r t t i'as'fs fcii lbhl: obo 500 b5 runs and of the yields and inspections of the reformate See footnotes at and f table products are given 1n Table III below.

Table III Run Number 4 5A 5B 6A 6B FCC Gasoline Boiling Range, F IBP-180 180-310 1s0-3r0 sin-BF 3lO-EP Charge to Reformer, Hydrogenated Fraction of Table II, Run No 1 2 2 3 3 Operating Conditions 2.0 3.0 3. 1.8 .0 Pressure, p.s.i.g 300 300 300 300 300 Average Catalyst Temperature, F 809 001 948 000 951 Hydrogen/Hydrocarbon Ratio:

a as .18; .a; S.c. Bbl 1, 0,5 7 Yields, percent by Volume of Reformer Charge:

Debutanizcd Reforninte 82. 5 77. 5 68. 6 96.5 88. 8 Pentnncs-Pentcncs- 39. 5 8. 8 8. 8 1.0 5. 6 Butanes-Butcncs 8. 7 8. S 11.9 0.9 3. 4 Net Aromatics ProducetL 6.4 31. 7 34. 0 7. 8 18.1 a 1a: a ogen, u. o Pt covery, percent by Weight 101. 3 97. 3 09. G 00. 6 0. 0 Hydrogen in Reactor Gas, Mol percent. 77. 3 84. 2 77.2 85. 0 78. 4

See footnotes at end of table.

Table III-Continued Run Number 4 5A 5B 6A 6B Yield: Percent by Volume of Untreated Fraction; Debutanized Reformate 86. 1 79. 7 70. 6 97. 7 89.9 Yield, Percent by Volume of Full-Range FOO Gasoline, Debutanized Reformate 35.6 34.0 30.1 15.6 14.3 Inspections: 1

Stabilized Reformate Gravity, API 75. 4 48. 4 42. 8 39.1 35. 8 Hydrocarbon Type, percent by Aromat 11. 4 55. 9 67. 6 57. 8 74. 5 Olefin 1. 7 1. 2 0.7 2. 4 1. 5 saturates--- 86.9 42. 9 31. 7 39. 8 24. Naphthenes--- 2. 4 3. 0 1.1 Paraifins 84. 36. 8 22. 9 Reid Vapor Pressure, Pounds 9. 6 7. 0 6.0 2. 0 3. 6 Distillation (ASTM D8654)- -Over Point, F 108 104 102 147 130 End Point, F 253 364 375 436 450 10% at, F 120 160 159 316 238 50 134 242 251 341 340 90 166 300 297 376 390 Recovery Percent 96. 6 98.5 98. 5 98.7 98.0 Debutanized Reformate-Knock Rating: 3 Motor Method, Octane N umber Clear 77.0 86. 5 91. 2 79. 9 89. 1 +3 cc.TEL 91.6 92.1 94.1 87.8 92.7 Research Method, Octane Numbe Clear 79. 2 98.0 101. 9 89. 3 101. 2 +3 cc. TEL 93. 7 103. 6 106. 0 97. 7 103. 5

1 Platinum-Alumina.

2 Yields are corrected to 100% weight balance.

8 Calculated from octane numbers of the stabilized reformate, the Wiese octane number extension scale.

Octane Numbers over 100 are in terms or Table III shows that the hydrogenated light fraction was the flow schemes of FIGURES 2 and 4 in which the middle not appreciably improved by reforming. The only octane rating of the reformed hydrogenated light fraction that was higher than the corresponding rating of the untreated light fraction was the motor (+3 cc. TEL) octane rating. However, the motor (+3 cc. TEL) octane rating of the reformed hydrogenated light fraction was not as high as that of the hydrogenated light fraction prior to reformmg. procedure of subjecting the light fraction only to hydrogenation and not to catalytic reforming.

Table shows that hydrogenation and subsequent catalytic reforming of the 180-310 P. fraction of the olefinic gasoline raised all octane ratings of the olefinic intermediate fraction markedly. For example, the research clear octane rating of the middle fraction was raised from 92.0 to 101.9 in run 5B which was carried out at the preferred reforming conditions. Run 5A was carried out at less suitable reforming conditions, namely, low hydrogen concentration and moderate temperature. However, even this run increased the research octane number from 92.0 to 98.0. In both reforming runs of the hydrogenated middle fraction the liquid product yield wasrather low, specifically 79.7 volume percent of the olefinic fraction in the 901 F. run 5A and 76.6 volume percent in the 948 F. run 5B. This shows that when high gasoline yield rather than high octane rating is the main consideration These results demonstrate the significance of my fraction is not catalytically reformed would be preferred. Table III shows that hydrogenation and reforming of the entire residual 310 F.-end point FCC gasoline fraction produced yields of debutanized reformate of 97.7 volume percent based on the olefinic fraction in the 900 F. run 6A and 89.9 volume percent in the 951 F. run 6B. Runs 6A and 6B both produced reformates of reasonably high octane ratings',-the octane ratings for the product of the 951" F. run 63 being higher than those for the product of the 900 F. run 6A.

In accordance with my invention I have subjected the hydrogenated 310 F.-end point fraction of run 3, Table II, to single-stage, batch, solvent extraction with diethylene glycol at 11:1 solven-t-to-oil ratio. The rafiinate and extract were separated from the solvent and the raffinate fraction enriched in nonaromatics was then subjected to catalytic reforming over a platinum-alumina catalyst containing a small amount of fluorine at a pressure of 500 p.s.i.g,'a space velocity of 2 vol./vol./hr., a hydrogen recycle ratio of about 6,000 standard cubiofeet per barrel in two reforming runs at temperatures of 898 and 948 F.-, respectively. Table 'IV below gives the properties of the aromatics-enriched extract fraction and the nonaromatics-enriched raflinate fractions obtained in the extraction stage, as well as the reaction conditions and product inspections for the two reforming runs conducted withthe rafi'inate fraction.

Table IV Run Number 7 8 9 Solvent Extraction of Hydrogenated 310 F.End Point Fraction Extract Rafiinate Fraction Fraction Charge Stock 1 Catalyst. E E Reforming Conditions:

Pressure, p.s.i.g 500 500 Space Velocity:

V ./Vol./Hr- 2.0 2.0 Wt./Hr./Wf 3.0 2. 9 Average Catalyst Temperature, F 898 948 Hydrogen/Hydrocarbon Ratio:

Mol./Mol 8. 0 7. 3 Cu. Ft./Bbl 6, 241 5, 645 Recycle Gas Treatment (I) (8) See footnotes at end of table.

Table I VCnt1nued Run Number 7 S 9 Solvent Extraction of Hydrogenated 310 F.End Point Fraction Extract Rafiinate Fraction Fraction Yields, Percent by Volume of Charge: 4

Debutanized Reiorruate 83. 7 76. 2 Pentane-P 6. 7 7. 6 Butane-Bu 8. 4 11.0 Net Aromatics Pro e 19. 7 23. 2 Gas, C1-C Cu. Ft./Bbl 232 392 Hydrogen, Cu. Ft./Bbl 420 436 Recovery, Percent by Weight 93. 3 95. 4 Hydrogen in Reactor Gas, Moi. Percent--- 84. 0 72. 1 Liquid Yield, Percent by Volume of Hydrogenated 310 F.E.P. Fraction of FCC Gasoline, Debutanlzed Reformate Plus Extract Products from Solvent Extraction 38. 5 61. 5 90. 0 85. 4 Liquid Yield, Percent by Volume of Untreated 310 I .E.P. Fraction of FCC Gasoline 4 Products from Solvent Extraction 39. 0 62. 3 Inspections:

Stabilized Reiormate- Gravity, API 30. 9 45.0 41. 9 38. 5 Hydrocarbon Type, Percent by Volunlgez thus 9 8 44 1 are Naphthencs 10. 6 19. 7 7 O n 3.9 1.1 0.8 Aromatics 79. 6 32. 3 61. 2 73. 1 Reid Vapor Pressure, Lbs 0. 1 0.0 4. 5 4. 5 Distillation (ASTM D-86-54):

Over Point F 306 316 113 113 End Point, F--- 410 388 458 498 Percent at: F 328 328 184 180 346 341 327 322 304 365 374 382 Recovery, Percent 99. 0 98. 7 98. 7 98.4 Debutanized Reiormate-Knock Ra Motor Method: Octane N o.--

Clear 88. 2 52. 5 86. 6 89.9 +3 cc. TEL 91.0 75. 0 91.0 95. 4 Research Method: Octane Clear 100. 9 64. 3 97. 7 101. 2 +3 cc. TEL 103. 2 81. 4 100.1 104. 2

1 Raifinate Fraction from Run 7. I Platinum-on-Alumina. 1 Dried with Solid Desiccant. 4 Yields are corrected to 100% weight balance.

It should be noted that the reforming runs 8 and 9 of 50 In runs 8 and 9 the rafiinate fraction was sub ected to Table IV were carried out at a higher pressure than the reforming runs 6A and 6B of Table III and used a different catalyst. In fact, the conditions for runs 6A and 6B of Table III were more favorable for a good yieldoctane relationship than the conditions for runs 8 and 9. Furthermore, it should be noted that the extraction stage (run 7) was carried out as a single-stage solvent extraction. Better separation of aromatics from nonaromatics would have been obtained by multi-stage solvent extraction. This is mentioned so that it will be understood that even though the results of reforming only the rafiinate, as recorded in Table IV, showed an improvement over the results of reforming the entire hydrogenated residual fraction, as recorded in Table III, the improvement would have been even greater had the same reforming pressure and catalyst been used in runs 8 and 9, as were used in runs 6A and 6B, and had a more eflicient extraction procedure been employed.

Table IV shows that the solvent extraction run 7 produced an extract fraction and a raflinate fraction of widely differing properties. Thus, the extract fraction contained 79.6 volume percent aromatics as compared with 32.3 aromatics in the raifinate fraction. The Research, clear, octane number of the extract fraction was 100.9 as compared with 64.3 for the rafiinate fraction.

catalytic reforming under conditions that differed mainly in the reaction temperature, run 8 being at the moderate temperature of 898 F. and run 9 being at the higher temperature of 948 F. The combined yield of the extract fraction from run 7 and the debutanizcd reformed raflinate fraction from run 8 was 90.0 volume percent, based on the hydrogenated 310 F.-end point fraction. The debutanized reformate (not including the extract) had a Research, clear, octane number of 97.7 as compared with 64.3 for the raifinate before reforming. In run 9 which was carried out at a higher temperature than run 8 the liquid yield of debutanized reformate plus the extract fraction from run 7 was 85.4 volume percent, based on the hydrogenated 310 F.-end point fraction. The debutanized reformate (not including the extract) had a Research, clear, octane rating of 101.2. These results show that a fraction of very high octane rating was separated by selective extraction from the hydrogenated olefinic bottoms fraction and that the low octane raflinate fraction from the extraction stage was greatly improved in octane rating by catalytic reforming.

Table V below lists the octane ratings of gasoline obtained by blending the extract fraction from run 7 with the reformed rafiinate fractions from runs 8 and 9.

gasoline, particular catalytic hydrogenation conditions, particular reforming conditions, and a particular method, namely, solvent extraction, for separating the hydrogenated bottoms fraction into a fraction enriched in nonaromatics and a fraction enriched in aromatics. It should be understood, however, that considerable variation is possible within the individual process stages, except as limited by the appended claims. I have already indicated that the catalytically cracked gasoline charge can in general be prepared by the known processes for catalytically cracking gas oil to produce olefinic gasoline and I have indicated in general the conditions and catalysts that can be used for hydrogenation of the olefinic gasoline or fractions thereof.

The reforming stage can also he carried out by any of the conventional procedures [for catalytically reforming straight run or hydrogenated naphtha fractions. In general, these known processes use catalysts comprising a minor amount of a hydrogenating component, such as one or more metals or oxides of metals from group VI or group VIII of the periodic table, such as platinum, molybdenum, chromium, tungsten or nickel, the hydrogenating component being supported on a porous carrier such as alumina, silica-alumina, silica-magnesia, or the like. The reforming operation is usually carried out by.

contacting the naphtha or gasoline fraction with the catalyst in the presence of hydrogen in a concentration from 1,000 to 20,000 s.c.f./bbl. at a temperature from 800 to 1050 F. and a pressure from 250 to 1000 p.s.i.g. This results in conversion of the gasolinenange hydrocarbons to hydrocarbons of higher octane rating without much change in average molecular weight.

' I have described solvent extraction as a preferred method of separating the hydrogenated residual fraction into a traction enriched in nonaromatics and a fraction enriched in aromatics and have described diethylene glycol as a preferred extracting solvent. Other suitable extracting solvents include dimethyl sulfoxide, triethylene glycol and polyethylene glycol. Other suitable methods for selectively separating the aromatics and nonaromaticsinclude adsorption separation methods, extractive crystallization and molecular sieve separation.

Obviously many modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof and therefore only such limitations should be imposed as are indicated in the appended claims.

i claim:

\1. The process for upgrading a gasoline consisting essentially of a full range, catalytically cracked, olefinic gasoline boiling in the range 100 to 430 P. which comprises cat-alytically hydrogenating said full range gasoline at a temperature of 500 to 800 F., a pressure of 200 to 800 p.s.i.g. and with a hydrogen concentration of 1,000 to 10,000 s.c.f./bbl., fractionally distilling the hydrogenated gasoline to produce a light fraction boiling from the initial boiling point of the hydrogenated gasoline to an end point of 175 to 195 R, an intermediate fraction boiling from about the end point of the light fraction to an end point of 290 to 320 F. and a residual fractionhoiling from about the end point of the intermediate fraction to the end point of the hydrogenated gasoline, subjecting said intermediate fraction to catalytic reforming in the presence of hydrogen, subjecting said residualfraction to solvent extraction, recovering from said solvent extraction a rafiinate fraction enriched in nonaromatics and an extract fraction enriched in aromatics and having essentially the same boiling range as said rafiinate fraction, subjecting said rafilnate fraction to catalytic reforming in the presence of hydrogen and blending the hydrogenated light fraction, the reformed intermediate hydrogenated fraction, the reformed rafiinate fraction of the hydrogenated residual fraction and the extract fraction of the hydrogenated residual fraction to produce a gasolineof high octane rating,

2. The process for upgrading a gasoline consisting essentially of a full range, catalytically cracked, olefinic of 500 to 800 F, a pressure of 200 to 800 psig. and

with a hydrogen concentration of 1,000. to 10,000 s.c.f./bbl., subjecting said residual fraction to catalytic hydrogenation at a temperature of 5 00 to 800 F., a pressure of 2 00 to 800 p.s.i.g. and with a hydrogen concentration of 1,000 to 10,000 s.c.f./bbl., subjecting the hydrogenated residual fraction to solvent extraction, recovering from said solvent extraction a rafiiuate fraction enriched in nonaromatics and an extract fraction enriched in aromatics and having essentially the same boiling range as said rafiinate fraction, subjecting said rafiinate fraction to catalytic reformingin the presence of hydrogen and blending the hydrogenated light fraction, the untreated intermediate fraction, the reformed raffin-ate fraction and the extract fraction of the hydrogenated residual fraction to produce a gasoline of high octane rating.

3. The process for upgrading a gasoline consisting essentially of a full range, catalytic-ally cracked, olefinic gasoline boiling in the range 100 to 430 F. which comprises fractionally distilling said gasoline to'produce a light fraction boiling from the initial boiling point to an end point of to F, anda bottoms fraction boiling from about the end point of the light fraction to the end point of the olefinic gasoline, subjecting said bottoms fraction to catalytic hydrogenation at a temperature of 500 to 800 F, a pressure of 200 to 800 p.s.i.g. and with a hydrogen concentration of 1,000 to 10,000 s.c.f./bbl., fractionally distilling the hydrogenated bottoms fraction to produce a hydrogenated intermediate fraction boiling, from the initial boiling point of the hydrogenated bottoms fraction to an end point of 290 to 320 F. and a hydrogenated residual fraction boiling from about the end point of the intermediate fraction to the end point of the hydrogenated bottoms fraction, subjecting the hydrogenated intermediate fraction to catalytic reforming in the presence of hydrogen, subjecting the hydrogenated residual fraction to solvent extraction to produce a raffinate fraction enriched in nonaromatics and an extract fraction enriched in aromatics and having essentially the same boiling range as said raffinate fraction, subjecting said rafiinate fraction to catalytic reforming in the presence of hydrogen and blending the untreated light fraction, the reformed intermediate hydrogenated fraction, the reformed rafiinate fraction of the hydrogenated residual fraction and the extract fraction of the residual fraction to produce a gasoline of high octane rating.

4. The process for upgrading a gasoline consisting essentially of a full range, catalytically cracked, olefinic gasoline boiling in the range 100 to 430 F. which comprises fractionally distilling said gasoline to produce overhead fraction boiling from the initial boiling point to an end point of 290 to 320 F. and a residual fraction, boiling from about the end point of the Overhead fraction V to the end point of the olefinic gasoline, subjecting said residual fraction to catalytic hydrogenation at a temperature of 500 to 800 F., a pressure of 200 to 800 p.s.i.lg. and with a hydrogen concentration of 1,000 to 10,000 s.c.f./ bb1., subjecting the hydrogenated residual fraction to solvent extraction and recovering a raffiuate fraction enriched in non-aromatics and an extract fraction enriched a in aromatics and having essentially the same boiling range as said rafiinate traction, subjecting said raffinate fraction to catalytic reforming in the presence of hydrogen and 13 Table V Run Number 8 9 Retormate Plus Extract Charge to Extraction, Hyldfiigenate eavy FC C Gasoline Stabilized Reformate Plus Extract Gravity, API

Vapor Pressure, Reid, Lb.

Debuttanized Reformate Plus Extra Knock Rating Mloqtor Method, Octane 0.. Clear +3 cc. TEL Research Method, 00-

tane N 0.:

Clear +3 cc. TEL

Comparison of the yield-octane relationships for the products of runs 8 and 9 as listed in Tables IV and V with the products of runs 6A and 6B as listed in Table II shows a marked superiority for my procedure of separating the hydrogenated 310 F.end point fraction and subjecting only the nonaromatics-enriched portion thereof to catalytic reforming instead of reforming the entire fraction as in runs 6A and 6B. The motor method octane numbers (+3 cc. TEL) of the products of runs 6A and 6B were 87.8 and 92.7, respectively. As shown in Table V the octane numbers of the blends of extract with a reformates from runs 8 and 9 had motor method octane numbers (+3 cc. TEL) of 92.0 and 93.4, respectively. The other octane ratings of the products of Table V were similarly superior to those of runs 6A and 6B. As previously mentioned, the superiority of the products of Table V would have been even greater had the reforming procedure in runs 8 and 9 been the same as in runs 6A and 6B. This can be stated with confidence inasmuch as I have determined previously that the use of the catalyst employed in runs 6A and 6B and the use of lower pressure results in a yield-octane relationship clearly superior to that ohtainable with the catalyst and higher pressure used in runs 8 and 9.

Advantages of each of the embodiments of my process shown in the drawing can be seen from the data of Tables I through V. Thus, the tables show that the procedure of FIGURE 1 greatly improved the olefinic gasoline. Considering the qualities of each fraction, the hydrogenated light fraction, as shown in Table II was greatly superior in motor method octane rating to the full range olefinic gasoline and to the untreated light fraction of the olefinic gasoline as shown in Table I. Furthermore, the leaded octane sensitivity of the hydrogenated light fraction Was zero. The catalytically reformed hydrogenated intermediate fraction of run A, as shown in Table III, was greatly superior to the full range FCC gasoline and to the untreated intermediate fraction of the FCC gasoline in all octane ratings. The leaded octane sensitivity was also considerably better than that of either the full range FCC gasoline or of its intermediate fraction. The similar reformate obtained in run 5B was even more superior to the untreated fractions. The product obtained from the residual hydrogenated fraction in FIGURE 1, namely, the blend of the aromatics-enriched extract and the reformed raifinate was also greatly superior to the starting materials as shown in Table V. Thus, the blends produced from the runs 8 and 9' reformates had motor and research octane numbers markedly superior to those of full range FCC gasoline or of the residual fraction thereof. Furthermore, the leaded octane sensitivities were 10.8 and 10.9, respectively, as compared with 14.5 for the full range FCC gasoline.

Referring to FIGURE 2, the hydrogenated light fraction will have the same properties as discussed in connection with FIGURE 1. The untreated middle fraction 14 has the properties shown in Table I. This fraction is of about the same quality as the full range olefinic gasoline and can suitably be passed to gasoline blending with the fractions which are upgraded. The product obtained from the bottoms fraction by hydrogenation, extraction and catalytic reforming of the raflinate has the excellent properties described above in connection with FIGURE 1. Thus, the procedure of FIGURE 2 has the advantages of producing a light fraction with a high motor octane rating and a bottoms fraction of very high octane rating but omits treatment of the middle fraction, so that in comparison with FIGURE 1 there is an improvement in yield and a lower processing expense although there is a sacrifice in the octane improvement which would be obtained by reforming the hydrogenated middle fraction as in FIGURE 1.

In FIGURE 3 the light fraction is untreated. It has the properties indicated in Table I. All of its octane ratings are higher than those of the charge stock, although the motor octane rating is not nearly so high as is obtained by the hydrogenation procedures of FIG- URES 1 and 2. The middle and heavy fractions receive the same treatment as in FIGURE 1, namely, the hydrogenation and reforming of the middle fraction and hydrogenation, extraction and reforming of the raffinate of the residual fraction. Thus, the procedure of FIGURE 3 has most of the advantages of FIGURE 1 but does not gain the motor octane improvement of the light fraction which is obtained by hydrogenation of this fraction in FIGURE 1.

FIGURE 4 represents the minimum upgrading in accordance with the invention but shows that a considerable improvement of the full range gasoline is accomplished by treating only the residual fraction thereof. This fraction, as in each of the other schemes, is hydrogenated and solvent extracted, the rafiinate then being cataly-tically reformed. This selective treatment of a narrow portion of the full range gasoline, provides an economical method of making a marked improvement in the overall gasoline.

The specific example describes particular initial and end points for the fractions formed in my process. However, as I have indicated, these can extend over certain mentioned ranges. Thus, the light fraction can have an end point from to F. The middle fraction, which has an initial boiling point of about that of the end point of the light fraction, can have an end point from 290 to 320 F. The residual fraction will have an initial point of about that of the end point of the middle fraction. Within these ranges certain specific cut points are preferred for certain modifications of the process. Thus, the end point of the light fraction of the olefinie gasoline is preferably at or near the upper end of the range 175-195 P. if the middle fraction is to be subjected to catalytic reforming. Giving the light fraction the highest end point will insure that at least part of the C branched chain parafiins, and especially the dimethyl pentanes, are recovered in the light fraction instead of in the middle fraction. This will avoid subjecting to eatalytic reforming branched chain heptanes which are already of high octane rating.

Similarly, if the middle fraction is not to be subjected to catalytic. reforming, as in FIGURE 2, it is preferred to give the residual fraction of the olefinic gasoline an initial boiling point at or near the lower end of the range 290-320 F. This will place the C normal paraffin, n-nonane, or at least part of the same, in the residual fraction from which it will subsequently be recovered with other nonaromatics and subjected to catalytic reforming. This will contribute to maximum upgrading of the charge stock because n-nonane, although a minor component, has a rather low octane rating and can be improved by reforming.

Ihe runs of the specific example described above used a particular cracking process for preparing the cracked blending the untreated overhead traction, the reformed References Cited in the file of this patent UNITED STATES PATENTS 2,324,295 Goldsby July 13, 1943 18 Laughlin Oct. 22, 1946 Oberfell Apr. 15, 1947 Hemmimger Dec. 7, 1954 V Oblad Mar. 1, 1955 Voorhies Dec. 2, 1958 Haensel Sept. 22, 1959 Annable et a1. Feb. 16, 1960 Muiiat et a1 July 26, 1960 

1. THE PROCESS FOR UPGRADING A GASOLINE CONSISTING ESOLINE BOILING IN THE RANGE 100 TO 430*F. WHICH COMPRISES CATALYTICALLY HYDROGENATING SAID FULL RANGE GASOLINE AT A TEMPERATURE OF 500 TO 800*F., A PRESSURE OF 200 TO 800 P.S.I.G. AND WITH A HYDROGEN CONCENTRATION OF 1,000 TO 10,000 S.C.F./BBL., FRACTIONALLY DISTILLING THE HYDROGENATED GASOLINE TO PRODUCE A LIGHT FRACTION BOILING FROM THE INITIAL BOILING POINT OF THE HYDROGENATED GASOLINE TO AN END POINT OF 175 TO 195*F., AN INTERMEDIATE FRACTION BOILING FROM ABOUT THE END POINT OF THEE LIGHT FRACTION TO AN END POINT OF 290 TO 320*F. AND A RESIDUAL FRACTION BOILING FROM ABOUT THE END POINT OF THE INTERMEDIATE FRACTION TO THE END POINT OF THE HYTDROGENATED GASOLINE, SUBJECTING SAID INTERMEDIATE FRACTION TO CATALYTIC REFORMING IN THE PRESENCE OF HYDROGEN, SUBJECTING SAID RESIDUAL FRACTION TO SOLVENT EXTRACTION, RECOVERING FROM SAID SOLVENT EXTRACTION A RAFFINATE FRACTION ENRICHED IN NONAROMATICS AND AN EXTRACT FRACTION ENRICHED IN AROMATICS AND HAVING ESSENTIALLY THE SAME BOILING RANGE AS SAID RAFFINATE FRACTION, SUBJECTING SAID RAFFINATE FRACTION TO CATALYTIC REFORMING IN THE PRESENCE OF HYDROGEN AND BLENDING THE HYDROGENATED LIGHT FRACTION, THE REFORMED INTERMEDIATE HYDROGENATED FRACTION, THE REFORMED RAFFINATE FRACTION OF THE HYDROGENATED RESIDUAL FRACTION AND THE EXTRACT FRACTION OF THE HYDROGENATED RESIDUAL FRACTION TO PRODUCE A GASOLINE OF HIGH OCTANE RATING. 